The present invention is concerned with regulation of evolutive pulps. Evolutive pulps are liquids in which a certain reaction resulting in a physical or chemical transformation takes place such as producing a solid phase or modifying the characteristics of the solid phase initially carried by said liquid. One example of evolutive pulp would be plaster powder mixed with water. This invention can be applied to the hydraulic binders industry, plaster industry and generally to any industry in which there is a need to control the flow rate of evolutive pulps carried through piping.
In order to cutoff, introduce variations, or regulate a liquid flow rate to a given value, the use of elastic shape-changing valves is widespread. Such valves consist of a rigid tubular housing and a cylindrical inner cell, such as a sleeve, with enough elastic property to change shape. Valve closing is achieved through compression of the elastic sleeve by either the mechanical effect of a screw-nut-flywheel mechanism or by the effect of a pressurized fluid, such as water or air, sent between the housing and sleeve. When no mechanical or pneumatic action is exerted upon the sleeve, the valve allows direct passage of the product at full rate of flow, when the sleeve is subjected to a shape-changing action, the aperture of the sleeve opening is reduced and the valve allows only a reduced flow rate of the product. With a sufficiently strong mechanical or pneumatic action, the elastic walls of the sleeve eventually become joined, thus completely closing the valve.
Such manually controlled valves are recommended for viscous, pasty or abrasive liquids. But in the case of evolutive pulps, deposits form in the narrow channel created by the compressed sleeve, deposits which change the size of the sleeve aperture alter the valve setting and eventually create an obstruction.
It is also known to pulsate elastic shape-changing valves to keep material in a liquid state and to use large elastic sleeves to break up solids.